ul,li {
    margin: 0;
    padding: 0;
    list-style: none;
}
    a {
    text-decoration: none;
}
.nav {
    position: relative;
    margin: 0 auto;
    width: 550px;
    font: 14px/1.5 '微软雅黑';
    opacity:0.65;
}
.block {
    position: absolute;
    z-index: 9;
    left: 0;
    top: 0;
    width: 0;
    height: 0;
    border-radius: 4px;
    background-color: #f00;
}
.nav-list {
    position: relative;
    z-index: 10;
    padding-left: 20px;
    overflow: hidden;
}
.nav-list .item {
    float: left;
    padding: 15px 20px;
}
.nav-list .item a {
    color: #fff;
}
